1. Field of the Invention
The present invention relates to the field of computer display systems. Specifically, the field of the invention relates to computer systems for displaying or printing textual, graphical, or other forms of information.
2. Related Art
In the current world of digital computers, visual imagery is often composed of a large number of dots or display elements. These display elements are also called picture elements or pixels. Individual pixels may only be in one of two states: active or inactive (i.e. lighted/unlighted or blackened/transparent or colored/uncolored or on/off). In color displays, pixels are considered to have a color value (i.e. a red, green and blue dot on a color display), however the color dots corresponding to a single pixel may be collectively considered a single pixel. Prior art systems have means for displaying gray scales or color; however, at some level, pixels are either active or inactive. Although individually each pixel is either active or inactive, on a larger scale the pixels combine to form textual, graphical, or other forms of information display or images.
Picture elements (pixels) are used on a wide variety of output devices. Such devices include video display screens, plasma display screens, dot matrix printers, laser printers, facsimile transceivers, and other display or print devices. On each of these display or print devices, pixels are arranged in rows and columns with a predetermined density appropriate for the particular application. Images presented to these output devices for display must be configured with the pixel density in mind in order to preserve the visual integrity of the image. Often, however, configuring an image for the preferred output density is not possible. For example, an image may be configured for one particular output device but displayed or printed on another device. In these situations, a conversion from one pixel density to another is required.
Although some density conversion techniques exist in the prior art, these techniques suffer from a variety of problems. For example, density conversion from a print image to a facsimile image presents a particularly difficult problem. An input print file may contain text data, graphics data, a combination of text and graphics, a combination of different text and graphics densities, and a variety of different text and graphics modes. In spite of these various forms of input image data, any conversion technique must correctly activate pixels for all text and graphics images regardless of the number and order of mode and/or density changes while maintaining the correct size and aspect of the image and all of its components after conversion. Conversion front one pixel density to another must be performed efficiently and quickly in a real-time system. For example, conversion front a printable image to a facsimile image must be perforated while a facsimile copy is being transmitted at 9600 baud. Prior art systems have been unable to achieve a high level of conversion accuracy within acceptable performance constraints.
Thus, a better means for converting from one pixel density to another density is required.